The present invention relates to biocidal-antifouling agents with low ecotoxicity index.
In particular, the present invention relates to the use of tetralin derivatives effective as biocidal and antifouling agents for preventing and slowing the growth of algae, molds and microorganisms.
Menadione and its derivatives are vitamin derivatives which have an antihemorrhagic activity and have long been used in the medical and veterinary field, as disclosed in U.S. Pat. No. 2,367,302.
In particular, adducts of menadione bisulfite with heterocycles such as triazine, pyrimidine, guanidine have been described in U.S. Pat. No. 3,328,169, while adducts of menadione bisulfite with pyridine derivatives are known from Italian Patent No. 1,097,391.
Up to now, the only indication for use of these menadione bisulfite adducts, salified with heterocyclic bases, has been based on their antihemorrhagic activity. Accordingly, these compounds have been applied in the veterinary field as medicines and as additives for feeds meant for farm animals and fish.
In JP 03-131669, Yokoi et al. provides antifouling coatings containing naphthoquinone and/or p-hydroxyquinone derivatives having a biocidal activity.
In JP 66-014238, a compound for treating skin infections, the formulation comprising menadione (2-methyl-1,4-naphtaquinone, i.e. vitamin K3) and curcumin dissolved in a solvent such as ethanol, is provided.
There was a need in the art for new biocidal agents, having improved antifouling properties with low antifouling toxicity.
Surprisingly, it has now been found that there is another unexpected indication for use of menadione bisulfite adducts salified with heterocyclic bases in a technical field which is entirely different from the one in which menadione derivatives are currently and commonly used.
Specifically, it has now been found surprisingly that these compounds have a great ability to inhibit and slow the deposition and growth of a layer of living organisms such as a layer of vegetation, mold or microorganisms on the surfaces of objects and structures exposed to humidity or immersed in fresh or salt water.
One of the aims of the present invention is to provide new indications for use for a group of compounds correlated to the menadione bisulfite heterocyclic base salts.
Another object is to provide biocidal and antifouling agents which are highly effective in preventing the adhesion of algae, molds and colonies of microorganisms on surfaces of objects and structures exposed to humidity or immersed in water.
Another object is to provide a class of compounds having a biocidal and/or antifouling activity which have minimal ecotoxicity and polluting activity and can therefore be used in the ecosystem without compromising its balance.
In view of this aim, these objects and others which will become apparent hereinafter, and in accordance with a first aspect of the present invention, use of menadione bisulfite adducts salified with organic bases as biocidal and/or antifouling agent is provided.
Within the scope of the present invention, the said derivatives are selected from the group consisting of menadione triaminotriazine bisulfite (I) (MTB) and menadione (bis) piperazine bisulfite (II) (MBP). The compounds according to the present invention are used as antifouling and biocidal agents having low ecotoxicity and minimal polluting activity with respect to the ecosystem.
The compounds according to the invention are used whenever materials, objects and structures need to be protected from the growth of vegetation or colonies of unwanted microorganisms. In particular, the compounds according to the invention are suitable to prevent and limit the growth of algae and molds on the surfaces of objects that make contact with water or with ambient moisture for prolonged periods of time.
In particular, these objects and structures include watercraft hulls, submerged masonry or metallic structures, floating transport or signaling means, fishing nets, and cooling systems which use seawater.
The materials that can be treated with the compounds according to the invention are materials of various origin, commonly used in the manufacture of items which make contact with fresh water or salt water, such as for example steel, concrete, glass, plastics, rubber, wood, textile fibers, leather, et cetera.
The use according to the present invention advantageously provides for the addition or application of an amount which is effective from an antifouling and/or biocidal standpoint of a compound of the above described type to a material or structure exposed to water or moisture.
The compounds according to the invention are also suitable in the prevention and slowing of mold growth.
For this use, the compounds according to the invention are advantageously added to water-based emulsion paints, to adhesives, cellulose-based glues, fluids for machining and cooling metals, lubricating fluids for spools of thread, systems and raw materials for the processing of paper and for the preservation of tanned hides.
It has also been found surprisingly that MTB and MBP according to the invention have a biocidal activity against the most disparate bacterial strains that form colonies on the above cited objects and structures.
The compounds of the invention are used in amounts which vary according to the type of application and can be easily determined by a person skilled in the field. Suitable concentrations for the use of the invention can vary from a few ppm (0.0001% by weight for use as antifouling in cooling water such as in power stations, steelworks) up to concentrations of 40%, by weight (formulation for antifouling paints). An effective biocidal concentration for menadione and derivatives thereof is advantageously in the range of 0.5% to 10% by weight, preferably of 1 to 5% by weight.
The compounds according to the invention can be applied pure or added to carriers, such as powders, nebulizing agents and dispersants, or can be dissolved or suspended in a liquid, and in this case they are usually accompanied by wetting agents or emulsifiers in order to promote uniform dispersion of the active principle.
In the case of use of MTB and MBP adducts as mold preventers for fluids such as lubricants used in the machining of metals or lubricants for spools of thread, cellulose-based adhesives, for example wallpaper, said adducts can be used in suspension or emulsion, associated with wetting agents or emulsifiers, preferably at concentrations between 3 and 15% by weight.
The compounds according to the invention are furthermore used in the preparation of formulations of antifouling paints preferably in amounts which can vary between 3 and 15% by weight, advantageously in association with base materials.
The base materials for antifouling paints include binding agents such as synthetic and natural resins, homo- and copolymers, synthetic and natural caoutchouc, acrylic polyurethane epoxy resins or preparations of monomers to be polymerized in place to which the antifouling agent is added.
The use of menadione bisulfite derivatives according to the invention allows to considerably limit the problems of pollution and ecotoxicity caused by the use, in marine paints, of antifouling agents which are usually based on heavy metal derivatives.
The compounds according to the invention have proved themselves highly toxic and repellent both against microorganisms which tend to form colonies and against algae and molds.
Differently from commonly used antifouling agents, which are based on heavy metals, the derivatives according to the invention, by having a common non-toxic vitamin matrix, are not a source of pollution for the environment.
This advantage is more evident when the compounds according to the invention are used in the cooling of industrial plants located in coastal regions, since in this case enormous amounts of water are treated with antifouling agents in order to avoid the growth of algae in the pumping piping.
The high antifouling effectiveness achieved at low dosage, together with the high biodegradability of the compounds according to the invention, can be noted in the low values of the ElI (Environmental Impact Index)=1xe2x88x92EC50/LC1 (menadione triaminotriazine bisulfite=xe2x88x921.84; menadione piperazine bisulfite=xe2x88x922,0), where:
EC50 is the concentration that inhibits by 50% the settling of the species of larva used as target;
LC1 is the minimum toxic concentration for the larvae used as target.
The lower the ratio between the two parameters, the less the product pollutes. Otherwise, higher values correspond to a higher likelihood of damaging the ecosystem in which the compound is active.
This index is an empirical value for giving a measurement of the toxicity of the tested components with respect to other organisms and also provides an index of polluting characteristics.
By subtracting this ratio EC50/LC1 from 1, the EII has a positive or negative value depending on whether antifouling effectiveness (EC50) becomes apparent before or after the minimum toxic concentration (LC1).
Clearly, products having EII values which are positive or in any case negative but close to zero are to be preferred over those which have negative EII values.
The following examples are provided merely as illustration of the present invention and must not be intended as limiting the scope thereof as defined in the appended claims.